1. ------IND- 2002 0400 S-- EN- ------ 20021106 --- --- PROJET
Statute Book of the Swedish
Maritime Administration
SJÖFS 2002:xx
Published
day month 2002
SFH
1.2.1.1
The Swedish Maritime Administration’s administrative
provisions and guidelines on Finnish-Swedish ice
classes
Adopted on day month 2002
The Swedish Maritime Administration lays down the following 1
pursuant to Chapter 2 Section 4 of the Order on ship safety (1988:594)
and adopts the following guidelines.
Chapter 1 Application
Section 1 These provisions shall apply to ships navigating Swedish
waters during the winter.
The following four ice classes shall apply to such ships:
Ice class IA Super
Ice class IA
Ice class IB
Ice class IC
Section 2 A new ship is a ship the keel of which is laid or on which
construction began on or after 1 September 2003.
1
This Regulation has been drawn up in cooperation between the maritime authorities in
Sweden and Finland.
These provisions have been notified in accordance with Directive 98/34/EC of the
European Parliament and of the Council of 22 June 1998 laying down a procedure for the
provision of information in the field of technical standards and regulations and of rules on
Information Society services (OJ L 204, 21.7.1998, p.37, Celex 398L0034), amended by
European Parliament and Council Directive 98/48/EC (OJ L 217, 5.8.1998, p.18, Celex
398L0048).
1
An existing ship is a ship the keel of which was laid or on which
construction began before 1 September 2003.
Section 3 If a ship, on account of its unusual proportions, hull shape,
propulsion arrangement or another property, has in practice an
abnormally poor ability to navigate in ice, the Swedish Maritime
Administration may reduce its ice class.
Section 4 The Swedish Maritime Administration may give its consent
for an existing ship to retain its original ice class even if it does not meet
the output requirements of Chapter 3 Sections 5 and 6, provided that the
ship has regularly called at ports in Sweden or Finland during the winter
and that the ship has shown a capacity to sail in ice which is considered
by the maritime administration in the respective country to be
satisfactory.
Section 5 In designing the ship’s structure, equipment and arrangements
important for the ship’s safety and function, the effect of temperature shall
be taken into account.
General guidance
Factors which should be taken into account include, for example, the
function of hydraulic systems, the risk of water pipes and tanks freezing,
starting of emergency diesel engines, strength of material at low
temperatures etc.
The temperature of the air can drop well below 0 C for long periods
and can occasionally drop to around –30 C.
Section 6 A ship which is approved under legislation in other Member
States within the European Union and European Economic Area shall be
deemed equivalent to a ship which meets the requirements in these
provisions, provided that an equivalent level of safety is obtained by
means of this legislation.
Chapter 2 Ice class draught
Maximum draught amidships
Section 1 The maximum ice class draught amidships shall normally be
taken as the summertime freshwater load line draught. If the ship has a
timber load line, the summertime freshwater load line with timber cargo
shall be used.
Maximum and minimum draught fore and aft
Section 2 The maximum and minimum draught fore and aft shall be
determined and indicated on the classification certificate.
2
SJÖFS 2002:xx
Section 3 The line determined by the maximum draught fore,
amidships and aft is called the load water line (LWL). This line may be
a broken line.
The line determined by the minimum draught fore and aft is called the
ballast water line (BWL).
Section 4 The draught and trim defined by the LWL must not be
exceeded when the ship navigates in ice. The salt content of the water
along the intended route shall be taken into account when the ship is
loaded.
Section 5 The ship shall always be loaded at least to the BWL when it is
navigating in ice. All ballast tanks situated above the BWL and required
for loading the ship down to this water line shall have arrangements for
preventing the water freezing.
Section 6 When the BWL is determined, account shall be taken of the
need to guarantee a reasonable capability to navigate in ice in ballast.
The propeller shall be fully under water and, where possible, fully under
the ice.
Section 7 The draught forward shall be at least:
(2 + 0.00025 Δ) ho [m], but need not be greater than 4 ho where
Δ = the ship’s displacement [t] with the maximum ice class draught
in accordance with Chapter 2 Section 1.
ho = thickness of the ice in accordance with Chapter 4 Section 6.
Chapter 3 Engine output
Section 1 The engine output P is the maximum power that the
propulsion machinery can continuously provide to the propeller(s). If
the engine output is restricted by technical means or by a regulation
which is applicable to the ship, this restricted output shall be P.
Requirements pertaining to engine output for ships of ice class IA
Super, IA, IB and IC.
Section 2 The engine output shall be calculated at the draughts which
correspond to the LWL and BWL. The engine output shall not be less
than either of these as determined by the following formula, and in no
case less than 1000 kW for ice classes IA, IB and IC and not less than
2800 kW for ice class IA Super.
Section 3 The ship dimensions defined below shall be measured at the
maximum ice class draught and ballast draught.
3

the ship’s length between the perpendiculars [m]
length of the bow [m]
length of the parallel midship section [m]
the ship’s maximum width [m]
maximum ice class draught LWL or ballast draught
BWL [m] in accordance with Chapter 2 Section 3
= the area of the bow’s water line [m2]
= the angle of aperture of the waterline at B/4 [degrees]
1
= the stem angle on the centreline [degrees]
2
= angle of the slope of the vertical towards the waterline at
L
LBOW
L PAR
B
T
A wf
=
=
=
=
=
B/4
DP
HM
HF
[degrees]
= propeller diameter [m]
= thickness of brash ice in the centre of the channel [m]
= thickness of the brash ice belt broken by the bow [m]
»Figure 1
Key to figure:
Vertikal vid B/4
«
If the ship has a bulb, 1 = 90
Vertical at B/4
In determining a ship’s parameters based on draughts, the actual
draught shall be used. T in the parameter DP /T relates to the draught on
the LWL. However, L and B are always determined on the LWL
draught.
Validity range
Section 4 The formulae for ice resistance contained in Chapter 3
Section 5 and 6 shall be applied when the ship’s parameters fall within
the minimum and maximum values in Table 1.
4
SJÖFS 2002:xx
Table 1.
Parameter

[°]
[°]
[°]
[m]
[m]
[m]
1
2
L
B
T
LBOW/L
LPAR/L
DP /T
Awf /(L·B)
Minimum
15
25
10
65.0
11.0
4.0
0.15
0.25
0.45
0.09
Maximum
55
90
90
250.0
40.0
15.0
0.40
0.75
0.75
0.27
If a ship’s parameters fall outside the values in Table 1, other methods
in accordance with Chapter 3 Section 7 shall apply for determining R CH.
General guidance
The formulae for ice resistance are, for natural reasons, semiempirical formulae and they therefore have a fixed validity range. It is
difficult to determine the limits of validity exactly. Table 1 shows the
ranges of the various parameters, which are included in the formulae.
New ships
Section 5 In order to obtain ice class IA Super, IA, IB or IC, new ships
shall meet the following requirements regarding engine output.
P  Ke
(R CH / 1000) 3/2
DP
kW  ;
where
where
:
Ke is determined as follows:
Type of propeller
or machinery
CP or electrical or
hydraulic machinery
FP
propeller
1 propeller
2.03
2.26
2 propellers
1.44
1.60
3 propellers
1.18
1.31
RCH is the ship’s resistance in a brash ice channel with a frozen top
layer:
5


3
 LT  A
2
R CH  C1  C2  C3C H F  H M  B  Cψ H F  C4 L PARH 2F  C5  2  wf
B  L
C = 0.15cos2 + sinsin, C shall be equal to or greater than
0.45
Cψ = 0.047 · ψ – 2.115 , and Cψ = 0 if ψ  45°
HF = 0.26 + (HMB)0.5
HM = 1.0 for ice classes IA and IA Super
= 0.8 for ice class IB
= 0.6 for ice class IC
C1 and C2 are coefficients for the frozen top layer in the channel and
may be set to zero for ice classes IA, IB and IC.
For ice class IA Super the following applies:
BL PAR
 1  0.021 1  f 2 B  f 3 L BOW  f 4 BL BOW 
2 T 1
B
T  B2

C 2  1  0.063 1  g 1  g 2 B  g 3 1  1.2 
B L

C1  f 1
For ships with bulb bow, 1 shall = 90.
f1 = 23
N/m2
g1 = 1530 N
f2 = 45.8 N/m
g2 = 170
N/m
f3 = 14.7 N/m
g3 = 400
N/m1.5
f4 = 29
2
N/m
C3 = 845 kg/(m2s2)
C4 = 42 kg/(m2s2)
C5 = 825 kg/s2
 tan  2 

 sin  
  arctan 
The following conditions shall apply:
3
LT
20   2   5
B 
6
SJÖFS 2002:xx
Existing ships
Section 6 In order to obtain ice class IA or IA Super, existing ships
shall meet the requirements in Chapter 3 Section 5.
If the hull parameters cannot be determined in accordance with
Chapter 3 Section 5, the following formula shall be used:
3
 LT  B
N
R CH  C1  C 2  C 3 H F  H M 2 B  0.658H F   C 4 LH 2F  C 5  2 
B  4
For ice class IA, C1 and C2 can be set to 0. For ice class IA Super,
ships with no bulb, the following applies:
BL
C1  f 1 T
 1.84f 2 B  f 3 L  f 4 BL 
2 B 1
T  B2

C 2  3.52g 1  g 2 B  g 3 1  1.2 
B L

For ice class IA Super, ships with bulbs, C 1 and C2 shall be calculated
as follows:
C1  f 1
BL
 2.89f 2 B  f 3 L  f 4 BL 
T
2 1
B
T  B2

C 2  6.67g1  g 2 B  g 3 1  1.2 
B L

f1 = 10.3 N/m2
g1 = 1530 N
f2 = 45.8 N/m
g2 = 170
N/m
f3 = 2.94 N/m
g3 = 400
N/m1.5
f4 = 5.8
C3 =
C4 =
C5 =
N/m2
460 kg/(m2s2)
18.7 kg/(m2s2)
825 kg/s2
3
 LT 
The following conditions shall apply: 20   2   5
B 
Other methods for determining Ke or RCH
Section 7 Instead of the above values for Ke or RCH, the Swedish
Maritime Administration may approve Ke and RCH values for individual
ships based on more precise calculations or model tests. Such approval
may be granted on condition that it can be retested if the ship’s actual
performance warrants this.
7
Ships shall be capable of doing at least 5 knots in a channel with brash
ice of the following thicknesses:
IA Super HM = 1.0 m and a frozen top layer of 0.1 m
IA
= 1.0 m
IB
= 0.8 m
IC
= 0.6 m
Requirements pertaining to engine output for existing ships of ice
class IB and IC
Section 8 The engine output must not be less than that given in the
following formula and in no case less than 740 kW for ice classes IB and
IC.
P = f1  f2  f3  (f4 ·Δ + Po) [kW], where
f1 = 1.0 for a propeller with fixed blades
= 0.9 for a propeller with rotatable blades
f2 = 1 /200 + 0.675 but not greater than 1.1.
The product f1  f2 shall not be less than 0.85
1 = the forward-pointing angle between the stem and LWL. If the
stem forms an even curve within the ice-strengthened area, as
defined in Chapter 4 Section 8, it may be represented as a
straight line between the intersection points of the stem with the
upper and lower limits of the ice-strengthened area. If the stem
forms a broken line, the highest value for 1 shall be used.
f2 = 1.1 for a bulb stem
f3 = 1.2 B/1/3 but not less than 1.0
f4 and Po shall be taken to be as follows:
IB
IC
 < 30000
f4
Po
0.22
370
0.18
0
IB
IC
  30000
0.13
3070
0.11
2100
 = the ship’s displacement [t] at the highest ice class draught in
accordance with Chapter 2 Section 1. The displacement need not
be greater than 80000 t.
Section 9 If the ship has properties which may be assumed to improve
the ship’s performance when navigating in ice, the Swedish Maritime
Administration may approve an engine output less than that required by
Chapter 3 Sections 5 and 6.
8
SJÖFS 2002:xx
Chapter 4 Hull construction
Section 1 The formulae and values given in this chapter for the
scantlings of parts of the hull may be replaced by more precise methods
if these have been approved by the Swedish Maritime Administration or
a classification society.
Section 2 If the scantlings obtained in accordance with these rules are
less than those required by a classification society for a nonstrengthened ship, the classification society’s rules shall be applied.
Section 3 The spacing and distances of ordinary stiffeners shall be
measured on a vertical plane parallel with the ship’s centreline.
However, if the ship’s side deviates more than 20° from the vertical plan
parallel with the centreline, the spacing and distances of the ordinary
stiffeners shall be measured along the side of the ship.
Section 4 The pressure of the ice may be higher on an ordinary stiffener
than on the plate in-between the ordinary stiffeners. The load distribution
is assumed to be as shown in Figure 2.
Figure 2
Ice load distribution on the side of the ship.
Regions
Section 5 The ship’s hull is divided into regions in accordance with
Figure 3.
Kan ej ändra här scannad bild.
9
Figure 3
Key to figure:
isbälte
ice-strengthened area
midskeppsområde
midship region
se 5 §
see Section 5
övre främre isbälte
upper fore ice-strengthened area
förskeppsområde
fore region
undre förskepp
fore foot
5 spantavstånd
5 ordinary stiffener spacings
gränslinje för den del av
border of part of hull where
skrovet där vattenlinjerna är
the waterlines are parallel to
parallella med centerlinjen
the centre line
Fore region: From the stem to a line parallel to and 0.04 L aft of the
forward borderline of the part of the hull where the waterlines are parallel
to the centreline. For ice classes IA Super and IA, the overlap with the
borderline need not be more than 6 metres, for ice classes IB and IC, this
overlap need not be more than 5 metres.
Midship region: From the aft boundary of the fore region to a line
parallel to and 0.04 L aft of the aft borderline of the part of the hull where
the waterlines are parallel to the centreline. For ice classes IA Super and
IA, the overlap with the borderline need not be more than 6 metres, for ice
classes IB and IC, this overlap need not be more than 5 metres.
Aft region: From the aft boundary of the midship region to the stern. L
is the regulation length applied by the classification society.
Ice loads
Height of the load area
Section 6 An ice-strengthened ship is assumed to navigate in icy
conditions in open sea corresponding to uniform ice with a thickness not
exceeding ho. The design height (h) of the area that is actually under ice
load at any particular time is, however, assumed to be only a fraction of
the ice thickness. The values of ho and h are given in the following
table.
Ice class
IA Super
IA
IB
IC
ho [m]
1.0
0.8
0.6
0.4
h [m]
0.35
0.30
0.25
0.22
10
SJÖFS 2002:xx
Ice pressure
Section 7 The design ice pressure shall be calculated using the formula:
p = cd  cl  ca  po [MPa], where
cd = coefficient taking into account the influence of the size and
engine output of the ship.
This coefficient shall be calculated using the formula:
cd 
ak  b
1000
k
ΔP
1000
a and b are given in the following table:
a
b

Fore
k  12
k > 12
30
6
230
518
Region
Midship & aft
k  12
k > 12
8
2
214
286
= the ship’s displacement at the maximum ice class draught
in accordance with Chapter 2 Section 1 [t]
P = the ship’s actual continuous engine output [kW]
cl = coefficient taking into account the probability of the design ice
pressure occurring
in a particular region of the hull for the ice class in question.
The value of cl is given in the following table:
Ice class
IA Super
IA
IB
IC
Fore
1.0
1.0
1.0
1.0
Region
Midship
1.0
0.85
0.70
0.50
Aft
0.75
0.65
0.45
0.25
ca = coefficient taking into account the probability of the entire
length of the region in
question being exposed
to pressure at the same time. This coefficient
shall be
calculated using the formula:
ca =
47 - 5l a
; maximum 1.0 ; minimum 0.6
44
la shall be taken to be as follows:
Structure
Type
framing
of la [m]
11
Shell
Ordinary
stiffeners
Transverse
Longitudinal
Transverse
Spacing of ordinary stiffeners
2 x spacing of ordinary stiffeners
Spacing of ordinary stiffeners
Longitudinal
Span of ordinary stiffeners
Span of ice side girders
2 x spacing of vertical primary
supporting members
Ice side girders
Vertical
primary
supporting
members
po = the nominal ice pressure; the value of 5.6 MPa shall be used.
The shell
Section 8 The vertical extension of the ice-strengthened area shall
comply with Figure 2 and be as follows:
Ice class
IA Super
IA
IB
IC
Above LWL
[m]
0.6
0.5
0.4
0.4
Below BWL
[m]
0.75
0.6
0.5
0.5
The following regions shall also be strengthened:
Fore foot: For ice class IA Super, the shell plates below the icestrengthened area between the stem and a position five ordinary stiffener
spaces aft of the point where the bow profile departs from the keel line
shall be at least as thick as the ice-strengthened area in the midship region
is required to be.
Upper fore ice-strengthened area: For ice classes IA Super and IA on
ships with a service speed in open waters of 18 knots or more, the shell
from the upper limit of the ice-strengthened area to 2 metres above this
and from the stem to a position at least 0.2 L aft of the forward
perpendicular shall in each case not have a thickness less than that
required in the ice-strengthened area in the midship region.
12
SJÖFS 2002:xx
General guidance
It is recommended that the fore part be strengthened in the
same way on ships with a lower service speed if, for example,
model tests have shown the ship to have a powerful bow wave.
Section 9 Sidescuttles must not be located in the ice-strengthened area.
If the weather deck in any part of the ship is situated below the upper
limit of the ice-strengthened area, e.g. in the deck well on a well decked
ship, the bulwark shall be at least as strong as the shell in the icestrengthened area is required to be.
The structure of freeing ports shall be sufficiently strong for the
purpose.
Plating thickness in the ice-strengthened area
Section 10 In the case of transverse framing, the plating thickness of
the shell shall be determined according to the following formula:
f l  p PL
+ t c [mm]
σy
t = 667 s
In the case of longitudinal framing, the plating thickness of the shell
shall be determined according to the following formula:
t = 667 s
p PL
+ t c [mm]
f 2  σy
s
= spacing of ordinary stiffeners [m]
pPL = 0.75 p [MPa]
p
= the ice pressure as given in Chapter 4 Section 7 [MPa]
1.3 
f1
=
f2
= 0.6 +
4.2
h/s  1.82
0 .4
h/s
; maximum 1.0
; if h/s  1
f2 = 1.4 – 0.4 (h/s); if 1  h/s < 1.8
h
= height of the load area as given in Chapter 4 Section 6 [m]
σy = the yield point of the material [N/mm2]; the following values
shall be used:
σy = 235 N/mm2 for steel for the hull construction of
normal
strength
σy = 315 N/mm2 for high strength
σy = 355 N/mm2 steel for hull construction
If steel with a different yield point is used, the actual yield point
may be used on condition that it is acceptable to the classification
society.
13
tc
= degree of abrasion and corrosion [mm]; normally tc shall be 2
mm.
If a special surface coating has been applied and is
maintained which
according to experience
can withstand abrasion from the ice, lower
values may be approved.
Ordinary stiffeners
Section 11 The vertical extension of the frame shall at least comply with
the following:
Ice class
Region
from the stem
to 0.3 L abaft
thereof
Above LWL
[m]
1.2
Below BWL
[m]
to the tank top
or below
the upper edge
of
IA Super
IA, IB, IC
abaft
0.3 L
from the stem
midship
aft
from the stem
to 0.3 L
abaft thereof
abaft
0.3 L
from the stem
midship
aft
1.2
the sills
1.6
1.2
1.2
1.0
1.6
1.2
1.6
1.0
1.3
1.0
1.0
1.3
1.0
Where an upper fore ice-strengthened area is required in accordance
with Chapter 4 Section 8, the ordinary stiffeners shall be ice strengthened
up to the height of this ice-strengthened area.
Where the ordinary stiffeners are required to be ice strengthened not
more than 250 mm beyond a deck or the top of a tank, the ice
strengthening may stop at this deck or tank top.
Transverse ordinary stiffeners
Section 12 The section modulus for a main or intermediate transverse
ordinary stiffener shall be calculated using the following formula:
Z=
psh l 6
10 [cm3]
mt  σy
14
SJÖFS 2002:xx
p
s
h
l
mt
=
=
=
=
the ice pressure as given in Chapter 4 Section 7 [MPa]
spacing of ordinary stiffeners [m]
height of the load area as given in Chapter 4 Section 6 [m]
span of ordinary stiffeners [m]
7 mo
7
- 5h/l
=
σy = yield point as per Chapter 4 Section 10 [N/mm2]
mo = coefficient, the value of which is given in the following table:
15
Key to figure:
Randvillkor
Exempel
Spant i ett bulkfartyg
med toppvingtankar
Spant som sträcker sig från
tanktaket till däcket på
ett enkeldäckat fartyg
Kontinuerligt spant mellan flera
däck eller vägare
Spant som sträcker sig endast
mellan två däck
Boundary condition
Example
Ordinary stiffeners in a bulk carrier
with top wing tanks
Ordinary stiffeners extending from
the tank top to the deck on a
single-decked ship
Continuous ordinary stiffeners
between several decks or side
girders
Ordinary stiffeners extending
between two decks only
The boundary conditions apply to both main and intermediate ordinary
stiffeners. The load is assumed to act mid-span.
Where less than 15% of the span, l, of the ordinary stiffener is within
the area of reinforcement in accordance with Chapter 4 Section 11, normal
scantlings of ordinary stiffeners may be used.
Upper end of the transverse ordinary stiffeners
16
SJÖFS 2002:xx
1. The upper end of the strengthened part of a main or an intermediate
ordinary stiffener shall be attached to a deck or an ice side girder in
accordance with Chapter 4 Section 16.
2. Where an ordinary stiffener terminates above a deck or ice side
girder located at or above the upper limit of the ice-strengthened area
in accordance with Chapter 4 Section 8, the part above this deck or
side girder may have the scantlings required by the classification
society for an unstrengthened ship. The upper end of the intermediate
ordinary stiffener may be connected to the adjacent main ordinary
stiffener by a horizontal member of the same scantlings as the main
ordinary stiffener. Such intermediate ordinary stiffener may also be
extended to the deck above. Where the deck above is more than 1.8
metres above the ice-strengthened area, the intermediate ordinary
stiffener need not be attached to this deck, except in the fore region .
Lower end of the transverse ordinary stiffener
1. The lower end of the strengthened part of an ice ordinary stiffener or
an intermediate ordinary stiffener shall be attached to a deck, tank
top or an ice side girder in accordance with Chapter 4 Section 16.
2. Where an intermediate ordinary stiffener terminates below a deck, a
tank top or an ice side girder located at or below the lower limit of
the ice-strengthened area in accordance with Chapter 4 Section 8, the
lower end may be connected to the adjacent main ordinary stiffener
by a horizontal member with the same scantlings as the main
ordinary stiffener.
Longitudinal ordinary stiffeners
Section 13 The section modulus for a longitudinal ordinary stiffener
shall be calculated using the following formula:
Z
f3  f 4  p  h  l 2
10 6 [cm3]
m  σy
The shear area of a longitudinal ordinary stiffener shall be:
A=
3 f3ph l 4
10 [cm2]
2σy
This formula shall only be used if the longitudinal ordinary stiffener is
attached to supporting structures using brackets as stipulated in Chapter 4
Section 14.
f3 = coefficient taking into account the distribution of load on
adjacent ordinary stiffeners
f3 = (1 – 0.2 h/s)
f4 = coefficient taking into account the concentration of load at the
point of support;
17
f4 = 0.6
p = the ice pressure as given in Chapter 4 Section 7 [MPa]
h = height of the load area as given in Chapter 4 Section 6 [m]
s
= spacing of ordinary stiffeners [m]. The spacing of ordinary
stiffeners shall not exceed 0.35 metres
for ice classes IA Super or IA and shall in no case exceed 0.45
metres.
l
= span of ordinary stiffeners [m]
m = boundary condition coefficient: m = 13.3 for a continuous
beam; where the boundary condition deviates significantly from a
continuous beam, e.g. in an end section, a lower boundary condition
coefficient may be used.
σy = yield point as per Chapter 4 Section 10 [N/mm2]
General provisions with regard to framing
Section 14 Within the ice strengthened section all ordinary stiffeners
shall be effectively attached to all supporting structures. A longitudinal
ordinary stiffener shall be attached to all vertical primary supporting
members and bulkheads using brackets. In the case of transverse ordinary
stiffeners which terminate against a side girder or a deck, a bracket or
similar construction shall be fitted. Ordinary stiffeners which cross loadbearing structural members shall be supported on both sides by means of
direct welding, collar plates or a supporting disc plate. A disc plate shall
be at least as thick as the web of the ordinary stiffener and its edge shall be
sufficiently strong to resist buckling.
18
SJÖFS 2002:xx
Section 15 For ice class IA Super and ice class IA in the fore and midship
regions the following shall apply in the ice-strengthened area:
1. Ordinary stiffeners which are not at a right angles to the shell shall be
supported to prevent tripping by means of brackets, intercostals,
stringers or similar at a distance not exceeding 1300 mm.
2. The ordinary stiffeners shall be attached to the shell by double
continuous welds. Scalloping is only permitted at welding seams in
the shell plate.
3. The web thickness of ordinary stiffeners shall be at least half that of
the shell plating and in any case not less than 9 mm. Where there is a
deck, tank top or bulkhead in lieu of an ordinary stiffener, the plate
thickness shall be as above to a depth corresponding to the height of
adjacent ordinary stiffeners.
Ice side girders
Girders within the ice-strengthened area
Section 16 The section modulus for a side girder located within the icestrengthened area in accordance with Chapter 4 Section 8 shall be
calculated in accordance with the following formula:
Z
f5  p  h  l 2
10 6 [cm3]
m  σy
The shear area shall be:
A=
p
h
3 f5ph l 4
10 [cm2]
2σy
= the ice pressure as given in Chapter 4 Section 7 [MPa]
= height of the load area as given in Chapter 4 Section 6 [m]
The product ph shall not be less than 0.30.
l
= span of side girders [m]
m = boundary condition coefficient in accordance with Chapter 4
Section 13.
f5 = coefficient taking into account the distribution of load on the
transverse ordinary stiffeners;
f5 = 0.9
σy
= yield point as per Chapter 4 Section 10
19
Ice side girders outside the ice-strengthened area
Section 17 The section modulus of a side girder located outside the icestrengthened area but supporting ice strengthened ordinary stiffeners
shall be calculated using the following formula;
 p  h l2
Z = f6
(1 - h s / l s) 10 6 [cm3]
m  σy
The shear area shall be:
3 f 6ph l
(1 - h s / l s) 10 4 [cm2]
2σy
= the ice pressure as given in Chapter 4 Section 7 [MPa]
= height of the load area as given in Chapter 4 Section 6 [m]
A=
p
h
The product ph shall not be less than 0.30.
l
= span of side girders [m]
m = boundary condition coefficient in accordance with Chapter 4
Section 13.
ls = distance to adjacent ice side girder [m]
hs = distance to ice-strengthened area [m]
f6 = coefficient taking into account the load distribution to
transverse ordinary stiffeners;
f6 = 0.95
σy = yield point of the material as per Chapter 4 Section 10
Narrow deck strips
Section 18 Narrow deck strips at hatches which serve as ice side girders
shall meet the requirements pertaining to section modulus and shear area
in Chapter 4 Section 16 and Chapter 4 Section 17, respectively. In the
case of very long hatches, the classification society may permit the
product ph to be taken to be less than 0.30, but in no case less than 0.20.
General guidance
Special attention is to be paid when designing weather deck hatch
covers and their fittings to the deflection of the ship sides due to ice
pressure in way of very long hatches .
Vertical primary supporting members
Load
Section 19 The load transferred to a vertical primary supporting
member from an ice side girder or from longitudinal ordinary stiffeners
shall be calculated using the following formula:
P
= f6  p  h  S [MN]
20
SJÖFS 2002:xx
p = the ice pressure as given in Chapter 4 Section 7 [MPa], where
the value of ca shall
however be calculated
assuming la to be equal to 2S.
h = height of the load area as given in Chapter 4 Section 6 [m]
The product ph shall not be less than 0.30.
S
= spacing of vertical primary supporting members [m]
In cases where the supporting ice side girder lies outside the icestrengthened area, the force F shall be multiplied by (1 – hs / ls ), where hs
and ls are as defined in Chapter 4 Section 17.
Section modulus and shear area
Section 20 Where a vertical primary supporting member follows the
structure model in Figure 4, the section modulus and shear area shall be
calculated using the following formulae:
Figure 4
Shear area:
A=
3 αQ
σy
10 4 [cm2]
α = as given in the table below
σy = yield point as per Chapter 4 Section 10
Q = calculated maximum cutting power for the load F in
accordance with Chapter 4 Section 19, or
k1F
where:
k1 = 1 + ½ ( lF / l )3 - 3/2 ( lF / l )2 or
= 3/2 ( lF / l )2 - 1/2 ( lF / l )3 whichever value is the greatest.
21
For the lower part of the vertical primary supporting members, the
smallest lF value within the ice-strengthened area shall be used, and for the
upper part the largest lF value within the ice-strengthened area shall be
used.
Section modulus:
Z=
M
σy

1
1 - (γ  A/Aa ) 2
10 6 [cm3]
22
SJÖFS 2002:xx
M = calculated maximum bending moment for the load F in
accordance with Chapter 4 Section 19
or k2Fl where:
k2 = 1/2 ( lF / l )3 - 3/2 ( lF / l )2 + ( lF / l )
γ
= as given in the table below
A
= required shear area where
kl = 1 + 1/2 ( lF/ l )3 - 3/2 ( lF/ l )2
Aa = actual cross-sectional area of the vertical primary supporting
member
Coefficients α and γ
Af /Aw

0
0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00
1.50 1.23 1.16 1.11 1.09 1.07 1.06 1.05 1.05 1.04 1.04

0
0.44 0.62 0.71 0.76 0.80 0.83 0.85 0.87 0.88 0.89
Af = cross-sectional area of the face plate
Aw = cross-sectional area of the web
Section 21 For arrangements and boundary conditions for a vertical
primary supporting member other than those specified in Chapter 4
Section 20, a direct stress calculation is to be performed.
The concentrated load on a vertical primary supporting member is given
in Chapter 4 Section 19.
The point of application shall in each case be selected so as to obtain the
maximum shear and bending moment, according to the arrangement of
side girders and longitudinal ordinary stiffeners.
The following stresses shall be applied:
Shear stress: τ = σ y / 3
Bending stress: σb = σy
 =  b2 + 3 2 =  y
Comparison stress: c
Fore part
Stem
Section 22 The stem shall be made of rolled, cast or forged steel or of
shaped steel plates.
General guidance
In order to improve the ship’s manoeuvrability in ice, a sharp edged stem
as per Figure 5 is recommended, particularly for smaller ships under
150 m in length.
23
Figure 5
Example of a suitable stem
Section 23 The plate thickness of a shaped plate stem shall be
calculated according the formulae in Chapter 4 Section 10, assuming
that:
s
= the spacing of elements supporting the plate [m]
pPL = p as defined in Chapter 4 Section 7 [MPa]
la = spacing of vertical supporting elements [m]
The same shall apply to all parts of the shell which form an angle of 30°
or more to the centreline in a horizontal plane in respect of a blunt bow.
The stem and the part of a blunt bow defined in paragraph 1 shall be
supported by floors or brackets spaced not more than 0.6 m apart and
having a thickness at least half that of the shell plate. The reinforcement of
the stem shall be extended from the keel to a point 0.75 m above the LWL
or, where an upper fore ice-strengthened area is required in accordance
with Chapter 4 Section 8, to the upper limit of this ice-strengthened area.
Arrangements for towing
Section 24 A mooring pipe with an opening not less than 250 mm by
300 mm, a length of at least 150 mm and an inner surface radius of at
least 100 mm shall be fitted in the bow bulwark on the centreline.
A bitt or other means of securing a towline, dimensioned to withstand
the breaking strength of the ship’s towline, shall be fitted.
Section 25 On ships with a displacement less than 30 000 tons, the part
of the bow extending to a height of at least 5 metres above the LWL and
at least 3 metres back from the stem shall be strengthened to withstand
the stresses caused by fork towing. For this purpose, intermediate
ordinary stiffeners shall be fitted and the framing shall be supported by
side girders or decks.
24
SJÖFS 2002:xx
Aft part
Section 26 On ships with two or three propellers, the ice strengthening of
the shell and framing shall be extended to the double bottom for at least
1.5 m forward and aft of the side propellers.
General guidance
An exceptionally small clearance between the propeller blade tip and
the stern frame should be avoided, as this may result in high loads on the
blade tip.
Section 27 Shafting and sterntubes of side propellers shall generally be
enclosed within plated bossings. If detached struts are used, their strength
and attachment shall be dimensioned so as to ensure adequate strength.
Section 28 A transom stern shall if possible not extend below the LWL.
If this cannot be avoided, the part of the transom stern below the LWL
shall be kept as narrow as possible. The part of the transom stern situated
within the ice-strengthened area shall be strengthened in the same way as
for the midship region.
General guidance
When dimensioning the hull of ships having propulsion arrangements
with rotatable thrusters or thrusters of the ‘azipod’ type, which provide
increased manoeuvrability, it should be taken into account that these
types of propulsion arrangements have been shown to produce a higher
ice load on the aft part and stern.
Bilge keels
Section 29 The attachment of a bilge keel to the hull shall be designed
so as to minimise the risk of damage to the hull if the bilge keel is torn
off.
General guidance
In order to limit the damage caused when a bilge keel is partly torn off
in ice, bilge keels should be divided into short, separate lengths.
Chapter 5 Rudders and steering arrangements
Section 1 The dimensioning of the rudder post, rudder stock, pintle,
steering gear and other parts of the steering arrangement, as well as the
capacity of the steering gear, shall be determined in accordance with the
class regulations. The maximum service speed for the ship used in these
calculations shall, however, not be less than the following values:
IA Super
20 knots
25
IA
IB
IC
18 knots
16 knots
14 knots
If the ship’s actual maximum service speed is higher, this speed shall be
used.
Section 2 For ice classes IA Super and IA, the rudder stock and the upper
edge of the rudder shall be protected against pressure from the ice by
means of an ice knife or similar means.
Section 3 Pressure control valves for hydraulics shall be able to
effectively deal with transient pressure variations. The scantlings of
steering gear components shall be such as to withstand the yield torque of
the rudder stock. Where possible, rudder stoppers working on the blade or
rudder head are to be fitted.
Chapter 6 Propellers, shafting and gears
Ice torque
Section 1 The ice torque shall be calculated using the following
formula:
M = m · D2
[Mpm], where:
D = propeller diameter in metres
m = 2.15 for ice class
= 1.60 for ice class
= 1.33 for ice class
= 1.22 for ice class
IA Super
IA
IB
IC
»If the propeller is not wholly under water when the ship is in
the ballast position, the ice torque for ice class IA shall be used for ice
classes IB and IC.
«
Propellers
Section 2 The elongation of the material used for propellers, measured
on a 5 diameter gauge length shall not be less than 19%. Its Charpy Vnotch impact strength shall be not less than 2.1 kpm at -10C.
26
SJÖFS 2002:xx
General guidance
It is recommended that the elongation of the propeller material be at
least 22%, measured on a gauge as above.
Section 3 The width c and the thickness t of cross-sections of the
propeller blade shall be determined such that:
a) at the radius of 0.25 D/2 for fixed pitch propellers
ct2 =
2.70
σb  (0.65 + 0.7  H/D)

20000
Ps
+ 22000  M
Zn

(13)
b) at the radius of 0.35 D/2 for propellers with rotatable blades
ct2 =
2.15
σb  (0.65 + 0.7  H/D)

20000
Ps
+ 23000  M
Zn

(14)

20000
Ps
+ 28000  M
Zn

(15)
c) at the radius of 0.6 D/2
ct2 =
0.95
σb  (0.65 + 0.7  H/D)
where: c
=
length, in cm, of the
expanded cylindrical section of the blade at
the radius in question
t = corresponding maximum thickness, in cm, at the radius in
question
H = pitch of the propeller, in m, at the radius in question. (For
propellers with rotatable blades, 0.7 Hnominell should be used)
Ps = shaft horse power in accordance with Chapter 3 Section 1.
N = speed of rotation of propeller, rev/min
M = ice torque, in accordance with Chapter 6 Section 1
Z = number of blades
σb = tensile strength of the propeller material, in kp/mm2
Section 4 The thickness of the blade tip, t, at the radius of 1.0 D/2 shall
be determined using the following formulae:
Ice class IA Super
t = (20 + 2D)
50
σb
mm
(16)
ice classes IA, IB and IC
t = (15 + 2D)
where:
50
σb
mm
(17)
D and sb are as defined above.
27
Section 5 The thickness of the other sections shall be determined by
means of a smooth curve connecting the thicknesses of the abovementioned sections.
Section 6 Where the blade thickness obtained is less than the regulation
thickness for the class in question, the latter shall be used.
Section 7 The thickness of the blade edges shall not be less than 50% of
the calculated thickness of the tip, t, measured at 1.25 t from the edge. In
the case of propellers with rotatable blades in conjunction with engines
which cannot be reversed, this shall only apply to the leading edge of
the blade.
Section 8 The strength of the blade-actuating mechanism located inside
a propeller with rotatable blades shall be 1.5 times greater than that of
the blade when the blade is assumed to be stressed at the radius of 0.9
D/2 in the weakest direction of the blade.
28
SJÖFS 2002:xx
Propeller shaft
Section 9 The diameter of the propeller shaft at its aft bearing must not
be less than
ds = 10.8
3
σ b  ct2
σy
(18)
where: sb =
tensile strength of the propeller
blade, in kp/mm2
2
ct = the value obtained from formula (13),
σy = yield point in kp/mm2 of the propeller shaft material.
If the diameter of the propeller hub is greater than 0.25 D, the following
formula shall be used:
d s = 11.5
3
σ b  ct
σy
2
(19)
where:
σb and σy are as defined above
ct2 = the value obtained from formula (14).
Section 10 If the diameter obtained for the propeller shaft is less than
the regulation diameter for the class, the latter shall be used. The end
diameters of the shaft may be reduced in accordance with the class
regulations.
Intermediate shafts
Section 11 The diameter, di, of intermediate shafts and thrust shafts
outside bearings must not be less than:
di = 1.1· dclassregulation for ice class IA Super
For ice classes IA, IB and IC, the regulation diameter shall be used.
Reduction gears
Section 12 When calculating the maximum permissible tooth load at
maximum shaft horse power Ps in accordance with Chapter 3 Section 1,
the following load factor, Ki, shall be used:
Ki = K
N
M  Ih  R 2
N+
I1 + I h  R 2
(20)
where: K =
class regulation load factor,
M = ice torque, in accordance with Chapter 6 Section 1
29
N = 0.716 Ps/n
where: Ps = shaft horse power in accordance with Chapter
3 Section 1.
n = corresponding engine speed, rev/min.
R = reduction factor; ratio of shaft’s incoming speed
and the shaft’s outgoing speed,
Ih = mass moment of inertia of the machinery components
rotating
at the higher rotational speed,
Il = mass moment of inertia of the machinery components
rotating
at the lower rotational speed. For the propeller an additional
30% is included
for water (Ih and I1 should be expressed in the same
dimension).
Chapter 7 Miscellaneous machinery requirements
Starting arrangements
Section 1 The capacity of the air receivers shall be sufficient to supply
air, without the need for replenishment, for not less than 12 consecutive
starts of the propulsion machinery, if this must be reversed for astern, or
6 consecutive starts if the propulsion machinery does not need to be
reversed for astern.
Section 2 If the air receivers also serve purposes other than starting the
propulsion machinery, they shall have sufficient extra capacity for these
purposes.
Section 3 The capacity of the air compressors shall be sufficient to load
the air receivers from atmospheric pressure to full pressure within one
hour. If the propulsion machinery for a ship of ice class IA Super needs
to be reversed for astern, the compressors shall be capable of loading the
receivers within 30 minutes.
Sea inlets and cooling water systems
Section 4 The cooling water system shall be designed to ensure the
supply of cooling water when the ship is navigating in ice.
For this purpose at least one cooling water inlet chest shall be
arranged as follows:
1. Cooling water inlets shall be situated near the centreline of the ship
and as far aft as possible.
2. As guidance for design, the volume of the chest shall be about one
cubic metre for every 750 kW engine output of the ship, including
30
SJÖFS 2002:xx
the power of the auxiliary machinery necessary for operation of the
ship.
3. The chest shall be sufficiently high to allow ice to accumulate above
the inlet pipe.
4. A pipe for discharging the cooling water, which permits discharge of
the entire cooling water capacity, shall be connected to the chest.
5. The area of the strum holes shall not be less than 4 times the inlet
pipe sectional area.
Section 5 Where there are difficulties in satisfying the requirements of
Chapter 7 Section 4(2) items 2-3, two smaller chests may be arranged
for alternate inlet and discharge of cooling water. The arrangement shall
otherwise comply with Chapter 7 Section 4.
General guidance
If heating coils are installed, they should be situated in the lower
or upper part of the chest. Arrangements for using ballast water
for cooling purposes may be accepted as a reserve in ballast
conditions.
This statute shall enter into force on 1 January 2003. The statute
repeals the Swedish Maritime Administration’s Decree (SJÖFS
1986:14) containing provisions on Finnish-Swedish ice classes.
Transitional provisions:
1. For ships which under the new provisions are classed as existing
ships and have ice class 1A Super and 1A, the older provisions shall
apply as regards engine output, but only up until 1 January 2005 or 1
January of the year 20 years after the ship was supplied, whichever is
the latest.
JOHAN FRANSON
(Maritime Safety Inspectorate)
Göran Liljeström
Issued by: Gunilla Blomqvist, Swedish Maritime Administration,
Norrköping, Sweden ISSN 0347-531X
31
CONTENTS
Chapter 1 Application
1
Chapter 2 Ice class draught
3
Maximum draught amidships
3
Maximum and minimum draught fore and aft
3
Chapter 3 Engine output
4
Requirements pertaining to engine output for ships of ice class IA
Super, IA, IB and IC.
4
Validity range
6
New ships
7
Existing ships
10
Other methods for determining Ke or RCH
11
Requirements pertaining to engine output for existing ships of ice class
IB and IC
11
Chapter 4 Hull construction
12
Ice loads
15
Height of the load area
15
Ice pressure
15
The shell
17
Plating thickness in the ice-strengthened area
19
Ordinary stiffeners
20
Transverse ordinary stiffeners
22
Longitudinal ordinary stiffeners
25
General provisions with regard to framing
26
Ice side girders
27
Girders within the ice-strengthened area
27
Ice side girders outside the ice-strengthened area
29
Narrow deck strips
29
Vertical primary supporting members
30
Load
30
Section modulus and shear area
30
Fore part
34
Stem
34
Arrangements for towing
36
Chapter 5 Rudders and steering arrangements
38
Chapter 6 Propellers, shafting and gears
38
Ice torque
38
Propellers
38
Propeller shaft
41
Intermediate shafts
41
Reduction gears
41
Chapter 7 Miscellaneous machinery requirements
42
Starting arrangements
42
Sea inlets and cooling water systems
42
ANNEX 1
45
32
SJÖFS 2002:xx
ANNEX 1
BASIS FOR CONTROL CALCULATION OF OUTPUT
REQUIREMENTS
In order to enable a control calculation of the output requirements, Table 2
gives the input data for a number of the types of ship.
Table 2
Example No.
Ice class
#1
#2
#3
#4
#5
#6
#7
#8
#9
IAS
IA
IB
IC
IAS
IAS
IA
IA
IB

°
24
24
24
24
24
24
36
20
24
1
°
90
90
90
90
30
90
30
30
90
2
°
30
30
30
30
30
30
30
30
30
L
m
150
150
150
150
150
150
150
150
150
B
m
25
25
25
25
25
22
25
25
25
T
m
9
9
9
9
9
9
9
9
9
LBOW
m
45
45
45
45
45
45
45
45
LPAR
m
70
70
70
70
70
70
70
70
70
Awf
m 
500
500
500
500
500
500
500
500
500
DP
m
5
5
5
5
5
5
5
5
5
1/CP
1/CP
1/CP
1/CP
1/CP
1/CP
1/CP
1/CP
1/FP
7838
4939
3477
2252
6797
6404
5342
5017
3870
8469
7645
6614
6614
2
No of propellers/ type
New ship
kW
Existing ship
kW 9198
6614
(calculated as per Chapter 3 Section 6)
33
Göran Liljeström, 011-19 13 29
Consequence analysis with regard to the
introduction of revised ice class regulations –
output requirements
1.
Description of the Regulations
The Regulations are directed at shipping companies, shipyards,
charterers and design engineers of tonnage intended for navigation
during the winter. The Regulations are common to Finland and Sweden.
2. Motivation for the draft Regulations
The ice breaker authorities in both Finland and Sweden have noted over
the years that, particularly the smaller tonnage ships, find it difficult to
follow the ice breaker even in brash ice channels. This experience has
led to adjustment of the output requirements for the two highest ice
classes.
3. Anticipated effect
Ships will be better able to navigate in ice and the assistance of the icebreaker will be more effective.
4. Costs
The Regulations are considered to result in a limited increase in costs
for smaller tonnage ships, whereas for larger tonnage ships there will a
reduction in costs, as engine output may be reduced.
5. Resource requirements
The proposed Regulations will not entail any increase in resource
requirements for the Maritime Safety Inspectorate.
6.
Training
34
SJÖFS 2002:xx
No additional training will be required for ship surveyors. Comments
and instructions for calculating output requirements will be published.
7. Environment
The Regulations will have no negative effect on the environment.
Göran Liljeström
35